1. Technical Field
The present invention relates generally to an improved data processing system and, more particularly, to an improved logically partitioned data processing system. Still more particularly, the present invention relates to an improved non-volatile random access memory access for logically partitioned data processing systems.
2. Description of Related Art
A logical partitioning (LPAR) functionality within a data processing system (platform) allows multiple copies of a single operating system (OS) or multiple heterogeneous operating systems to be simultaneously run on a single data processing system platform. A partition, within which an operating system image runs, is assigned a non-overlapping sub-set of the platform""s resources. These platform allocable resources include one or more architecturally distinct processors with their interrupt management area, regions of system memory, and I/O adapter bus slots. The partition""s resources are represented by the platform""s firmware to the OS image.
Each distinct OS or image of an OS running within the platform are protected from each other such that software errors on one logical partition cannot affect the correct operation of any of the other partitions. This is provided by allocating a disjoint set of platform resources to be directly managed by each OS image and by providing mechanisms for ensuring that the various images cannot control any resources that have not been allocated to it. Furthermore, software errors in the control of an OS""s allocated resources are prevented from affecting the resources of any other image. Thus, each image of the OS (or each different OS) directly controls a distinct set of allocable resources within the platform.
Currently, some resources existing singly within the data processing system are shared by more than one partition. It would be desirable to have a mechanism by which these single resources may be logically partitioned and have the logical partitioning strictly enforced.
The present invention provides a method, system, and computer program product for enforcing logical partitioning of a shared device to which multiple partitions within a data processing system have access. In one embodiment, a firmware portion of the data processing system receives a request from a requesting device, such as a processor assigned to one of a plurality of partitions within the data processing system, to access (i.e., read from or write to) a portion of the shared device, such as an NVRAM. The request includes a virtual address corresponding to the portion of the shared device for which access is desired. If the virtual address is within a range of addresses for which the requesting device is authorized to access, the firmware provides access to the requested portion of the shared device to the requesting device. If the virtual address is not within a range of addresses for which the requesting device is authorized to access, the firmware denies the request.